It is sometimes desirable to have access to ice or an ice substitute such as a frozen gel refrigerant in remote locations far removed from an electrical power supply. It may be possible to transport ice to such a remote area, but transporting ice to a remote area may be impractical in many situations. Thus, it is desirable in some instances to have the capability of freezing water or some other target material at a remote location without the use of electrically powered refrigeration devices.
U.S. Pat. No. 5,715,691 and U.S. Pat. No. 5,878,595, to the present inventor, each discloses a refrigeration arrangement and process employing pressurized ammonia as a working fluid to produce ice using only a heat source and no external power. The entire content of each of these prior patents is incorporated herein by this reference. The present invention represents a further improvement on the apparatus and processes disclosed in these to earlier patents. In particular, the present invention provides for better heat transfer from water or other material being frozen.